1. Field Of The Invention
This invention relates generally to a method of making a metallurgically improved metal casting and the apparatus by which the method is practiced. More particularly, the present invention relates to the art of making a metallurgically improved metal casting with increased productivity by quiescently feeding molten metal from a source thereof into a molding chamber through an in-gate situated below the top of the molding chamber.
2. Background Art
In the past, various types of molding equipment have been used to produce premium quality castings made of a variety of metals, including aluminum. The objective of such equipment generally is to provide a system which meets the objectives of generating a quality product at an acceptable cost.
Previous approaches have been made to the challenge of achieving premium quality cast aluminum parts. Illustrative of such approaches is that disclosed in U.S. Pat. No. 4,733,714 which is assigned to Cosworth Research & Development, Ltd., and which issued on Mar. 29, 1988, the disclosure of which is herein incorporated by reference. While the method and apparatus disclosed therein offers some advantages in achieving acceptable castings, the process is inherently slow and time-consuming. That process, which involves filling a mold "from the bottom" and holding pressure until casting solidification is achieved, limits production to relatively few castings per hour. One of the impediments imposed by such prior art techniques to the goal of achieving a higher throughput is the relatively and complex large equipment mass that must be moved by multiple stations in each cycle. Until the present invention, there remained unsolved the problem of designing a manufacturing facility which exploits the quality achievable by such processes while producing castings at an acceptable rate and cost.
Prior art solutions, such as that disclosed in U.S. Pat. No. 4,733,714 include relatively complex design concepts, which result in only a fair level of reliability. The intricacy of system design often makes lubrication and maintenance more difficult than these essential tasks should be.